The present invention relates generally to illumination devices, and more particularly, to a method and system for controlling operation of illumination devices.
Incandescent and fluorescent lights have been used as light sources in commercial and domestic applications. However, with significant investment by manufacturers and an increased demand from consumers to develop efficient lighting systems, light emitting diodes (LEDs) have become an attractive as well as an economic option.
LEDs are being used as single light sources as well as a part of an array of light sources. Arrays of LEDs are utilized to generate light over the visible spectrum. Light from different LEDs in the array are mixed to generate a desired color from the array of LEDs. For example, in an LED panel, multiple LEDs emitting red light, green light, as well as blue light may be present. The LED panel is coupled with control electronics such that appropriate colored LEDs are activated to produce desired colors. Further, the intensity of light emitted by the red LEDs, blue LEDs, and green LEDs may also be controlled to generate desired colors. Such control requires accurate determination of light emitted by each LED in the LED panel. Further, due to continued usage of an installed LED panel, it is possible that some LEDs from the panel do not emit light of the desired intensity and/or wavelength and thus lead to a deviation in the desired color output of the LED panel.
Control systems are employed with current lighting systems to adjust the intensity of light emitted by the LEDs. Control systems are also configured to determine the color emitted by the LEDs and adjust the colors when any or all of the LEDs emit colors that are different from their prescribed colors. Determination of color emitted by a light source involves determining the coordinates of the color in a color space. Examples of color space include, but are not limited to, International Commission on Illumination (CIE) 1931, and CIE 1976. Further, color determination may also include determination of a Correlated Color Temperature (CCT) of the light source. The CCT value of a light source is an indicator of apparent “warmth” or “coolness” of the light emitted by the light source. CCT is typically expressed as a single number with Kelvin (K) as the unit of measurement. For commercially available light sources, manufacturers typically specify the color points as well as the CCT value for the light source.
Control systems are designed to maintain the emitted light within the prescribed range for CCT as well the color points. Manufacturers may provide a typical aging curve for lighting systems to indicate the change in both intensity and color point of the light source with an increase in operational time. However, in case of LED light sources, the aging curve may not be accurate since existing LED aging patterns have not been widely accepted.
Current systems and methods involve determination of color point and CCT values for a light source based on images of the light source and image processing techniques. However, these systems require imaging systems that are highly accurate. Also the image processing techniques, utilized to process high resolution images of the imaging systems, require high speed processing capabilities. These requirements add to the cost of controlling operations of lighting systems. Systems that are economical in terms of selection of components tend to compromise of accuracy of characteristic estimation. Accuracy in characteristic estimation is paramount to the determination of colors and the actions that need to be initiated to keep the light emitted by the light source in the prescribed color range.
Hence, there is a need for a system and a method that effectively determines color characteristics of illumination sources.